1. Technical Field
The present invention relates to an optical pressure-sensitive adhesive sheet to be used in lamination of an optical member, manufacture of an optical product, or the like.
2. Background Art
Recently, in various fields, display devices such as a liquid crystal display (LCD) or an input device used by combining with the display device, such as a touch panel, has been widely used. In manufacturing of the display device or the input device, a pressure-sensitive adhesive sheet (pressure-sensitive adhesive tape) is used for laminating an optical member. For example, the transparent pressure-sensitive adhesive sheet is used for laminating the touch panel and various display devices or optical members (e.g., a protective plate) (for example, see Patent Documents 1 to 3).
As the application of display devices or input devices is expanded, pressure-sensitive adhesive sheets used in these devices have been required not only to have high transparency in a normal state but also to maintain the high transparency even under various environments. Specifically, it is required that whitening (white turbidity) should not occur due to humidification (for example, due to preservation under a high-temperature and high-humidity environment), and an appearance of an optical member, an optical product or the like to which the pressure-sensitive adhesive sheet is laminated or visibility of a display part (image display part) should not be deteriorated.
As a pressure-sensitive adhesive for directly laminating to a filter for a plasma display, the pressure-sensitive adhesive in which whitening hardly occurs even due to the humidification has been proposed (see Patent Document 4).    Patent Document 1: JP 2003-238915 A    Patent Document 2: JP 2003-342542 A    Patent Document 3: JP 2004-231723 A    Patent Document 4: JP 2004-263084 A